The invention lies in the field of conveying and further processing of flat (two-dimensional) products, particularly printed products. The invention relates to a device for separating product parts of a multi-part, flat product, including a receiving unit for receiving a product, and methods for separating the product parts, wherein the receiving unit includes a first and a second friction element which are movable relative to one another, wherein the two friction elements are arranged on the receiving unit in a manner such that the product can be arranged and firmly clamped between the friction elements, and the friction elements are designed in a manner such that the static friction between the product part and the friction element assigned to this is greater than the static friction between the product parts, so that the product parts can be moved with respect to one another given a relative movement between the two friction elements firmly clamping the product.
The invention also relates to a method for separating the product parts of a multi-part, flat product amid the use of the device.
Folded printed products are featured by a fold edge, along which the printed product is folded and which forms a first and a second product part. The free edges of the product parts are arranged opposite to the fold edge.
Folded printed products, in the course of their further processing, as a rule must be opened at least once, in order to insert further printed products, such as newspaper parts, pamphlets, brochures, flyers or goods samples or other further, as a rule, flat supplements, between their product parts.
It is common for the one product part to include a so-called overlap, in order to simplify the opening of folded products or to render it possible at all. The overlap is a surface section on one of the product parts in the region of the free edge lying opposite to the fold edge. The so-called surface section is featured in that this projects beyond the free edge of the other product part. The one product part thus with respect to the other part forms an exposed region.
The overlap can be created for example by way of incorporating a fold which is arranged asymmetrically, i.e., in an out-of-centred manner.
Such an overlap thus permits the gripping or fixing for example of the one product part on the overlap, e.g., by way of a clip. The two product parts then for example can be moved apart in a manner supported by gravity, wherein the other product part must be held. The printed product can be quickly and simply opened in this manner.
At this location, the European patent publication EP 2 297 014 B1 is to be mentioned as representative for a multitude of patent applications which have opening devices operating according to the opening principle defined above, as their subject matter.
The document EP 2 297 014 B1 describes a device for opening and inserting flat objects into a folded printed product. The device includes a circulating system with a plurality of compartments which are movable about a rotation axis along a closed, circular circulating path. The compartments include compartment bases which are delimited in the circulating direction by way of partition walls. The compartments moreover along the periphery include openings for inserting the printed products. The compartments in each case include a clip, by way of which the overlap of a trailing product part is firmly held on the trailing compartment wall.
The compartments are led downwards along an arched path, wherein the compartment openings on the outer periphery are moved downwards. With this procedure, the leading product part on account of gravity pivots downwards onto the oppositely lying, leading compartment wall, whereas the trailing products part is held by the clip limbs on the trailing compartment wall. The printed product opens, and the supplement can be inserted in this manner.
Since, as a rule, an overlap is not desirable with the end product, for example with a newspaper ready for dispatch, this must be eliminated at the end of the processing. This as a rule is effected by way of a cutting procedure. A high quantity of waste in the form of paper strips arises with this processing step.
The creation of an overlap for the simplification of the processing of printed products causes a significant quantity of cut waste which must be disposed of with a corresponding expense. Moreover, suitable assemblies are to be provided, which are capable of separating away the overlap again. Apart from ecological aspects, from an operational economical point of view, it is also the additional consumption of raw material and thus the additional costs which are important, without an additional use resulting therefrom with the end product.
If one could make do without an overlap in the further processing, then this would mean a significant saving of material. The saving of material as a result would lead to a reduction of production costs. Moreover, such a material saving would also contribute to taking care of resources. Moreover, a working step which contains the separating away of the overlap could also be omitted due to making do without the overlap.
Since the overlap as a rule merely serves for opening the printed product, as a result a device which is in the position of opening printed products without an overlap would be quite useful. Thereby however, one should consider the fact that the opening of the printed products is not only a very important, but also a very delicate method step. The opening and the holding-open of the products specifically on the one hand should be effected in a rapid and reliable manner, but on the other hand the product should be treated as gently as possible with this procedure, so that it is not damaged.
Thus the document EP 0 600 216 A1 with FIG. 8 describes a device and a method for opening a two-fold printed product without an overlap. For this, a vacuum is applied onto the outer surface of a first product part by way of a vacuum source. The first product part is held on a gripper tongue due to the produced suction pull, whilst the oppositely lying second product part moves away from the first product part on account of gravity. The installation and the operation of a vacuum device with vacuum conduits to the respective active locations however are extremely cumbersome and prone to disturbance. This is particularly the case with those operational types, with which the product must be opened during the conveying movement.